This invention relates to N-substituted aniline derivatives, more specifically to the compounds represented by the general formula (1) which have an inhibitory effect on nitric oxide synthase (NOS) to suppress the production of nitric oxide (NO) and thereby prove effective against the pathology in cerebrovascular diseases, in particular, occlusive cerebrovascular diseases in which excessive NO or NO metabolites would be involved, as well as traumatic brain injuries, seizure, headache and other pains, morphine tolerance and dependence, Alzheimer""s disease, Parkinson""s disease, septic shocks, chronic rheumatoid arthritis, osteoarthritis, viral or nonviral infections and diabetes; the invention also relates to possible stereoisomers and optically active forms of the compounds, pharmaceutically acceptable salts thereof, as well as to preventives and therapeutics containing them as an effective ingredient.
Occlusion or lower perfusion pressure in a cerebral artery or carotid artery by a certain mechanism cause ischemic necrosis in the brain tissue and this state is called xe2x80x9ccerebral infarctionxe2x80x9d. Cerebral infarction is roughly classified to cerebral embolism and cerebral thrombosis depending upon the mechanism involved.
Cerebral embolism is characterized by the formation of thrombi in a cerebral artery due to detachment of intracardiac blood clots or rarely blood clots on arterial walls, and cerebral thrombosis is primarily based on sclerotic lesions of cerebral arteries, which are complicated by an increased blood viscosity or a reduced perfusion pressure to result in an occlusion of the artery, which may progress to ischemic necrosis of the brain tissue (xe2x80x9cNOKEKKAN SHOGAIxe2x80x9d, compiled under the supervision of Hisao MANABE and Teruo OMAE, published by Life Science, pp. 54-55, 1992).
Irrespective of whether the cause is cerebral embolism or thrombosis, the formation of edema is observed in the ischemic brain tissue either concurrently with or prior to the development of the infarction. Vasogenic brain edema is manifested several hours after the onset of cerebral ischemia and continues for about one week from the onset. Thereafter, the brain edema decreases gradually and, depending on the area of the infarction, the edema persists as an infarct area in one to three months. Since the brain is covered with the rigid skull, brain edema causes an increase in the brain volume. If the brain edema exceeds a certain limit, there occurs an abrupt increase in the tissue pressure and the intracranial pressure, often inducing fatal hernia and eventually aggravating the brain damage to determine the scope of the subsequent infarct volume (xe2x80x9cCT, MRI JIDAI NO NOSOTCHUGAKU, PART I in Two Volumesxe2x80x9d, Kenji INAMURA and Akio TERASHI, published by Nihon Rinshosha, pp.,231-239, 1993). In addition, if a region of the brain becomes infarcted, the functions that have been fulfilled by the affected area, for example, perception, sensation and memory will be lost.
Thus, the treatment of brain edema and infarction which are critical to the quality of patient""s life and the prognosis of his disease is clinically a very important objective. As for brain edema, the currently used methods of treatment rely upon hyperpnea, the drainage of cerebrospinal fluid and the use of hypertonic solutions, steroids and others; however, in almost all the effects of cases, these methods are only transient and there is not much promise for the therapeutic efficacy to be finally achieved (xe2x80x9cNOSOTCHU CHIRYO MANUALxe2x80x9d, ed. by Masakuni KAMEYAMA, published by Igaku Shoin, pp. 34-36, 1991). Therefore, it has been desirable to develop drugs that are operated by an entirely different mechanism than the conventional etiological observation and which will prove effective in the treatment of ischemic cerebrovascular diseases.
A presently dominant theory based on genetic DNA analyses holds that NOS exists in at least three isoforms, namely, calcium-dependent N-cNOS (type 1) which is present constitutively in neurons, calcium-dependent E-cNOS (type 3) which is present constitutively in vascular endothelial cells and apparently calcium-independent iNOS (type 2) which is induced and synthesized by stimulation with cytokines and/or lipopolysaccharides (LPS) in macrophages and many other cells (Nathan et al., FASEB J. 16, 3051-3064, 1992; Nagafuji et al., Mol. Chem. Neuropathol. 26, 107-157, 1995).
A mechanism that has been proposed as being most probable for explaining the brain tissue damage which accompany cerebral ischemia is a pathway comprising the sequence of elevation in the extracellular glutamic acid level, hyperactivation of glutamic acid receptors on the post-synapses, elevation in the intracellular calcium level and activation of calcium-dependent enzymes (Siesjxc3x6, J. Cereb. Blood Flow Metab. 1, 155-185, 1981; Siesjxc3x6, J. Neurosurg. 60, 883-908, 1984; Choi, Trends Neurosci. 11, 465-469, 1988; Siejxc3x6 and Bengstsson, J. Cereb. Blood Flow Metab. 9, 127-140, 1989). As already mentioned, N-cNOS is calcium-dependent, so the inhibition of abnormal activation of this type of NOS isoform would contribute to the neuroprotective effects of NOS inhibitors (Dawson et al., Annals Neurol. 32, 297-311, 1992).
As a matter of fact, the mRNA level of N-cNOS and the number of N-cNOS containing neurons start to increase early after cerebral ischemia and their temporal alterations coincide with the development of infarction in rats (Zhang et al., Brain Res. 654, 85-95, 1994). In addition, in a mouse model of focal cerebral ischemia, the percent inhibition of N-cNOS activity and the percent reduction of infarct volume correlate to each other at least in a dose range of L-NNA that reduces infarct volume (Carreau et al., Eur. J. Pharmacol. 256, 241-249, 1994). Further in addition, it has been reported that in N-cNOS knockout mice, the infarct volume observed after focal cerebral ischemia is significantly smaller than that in the control (Huang et al., Science 265, 1883-1885, 1994).
A report has also been made that suggests the involvement of iNOS in the mechanism for the occurrence and development of ischemic brain damage. Briefly, after 12 hours of focal cerebral ischemia in rats, the mRNA of iNOS started to increase in the cerebral cortex of the affected hemisphere and, after 2 days, it reached a maximum concomitantly with iNOS activity, probably originating from polynuclear leukocytes (Iadecola et al., J. Cereb. Blood Flow Metab. 15, 52-59, 1995; Iadecola et al., J. Cereb. Blood Flow Metab. 15, 378-384, 1995). It has been reported that when NG-nitro-L-arginine methyl ester (L-NAME) which is one of the NOS inhibitors was administered after 3 hours of ischemia in consideration of the above-described temporal changes, the infarct volume decreased significantly (Zhang et al., J. Cereb. Blood Flow Metab. 15, 595-601, 1995).
Further in addition, it has been reported that the amount of occurrence of iNOS or its enzymatic activity increased in astrocytes or brain microvessels after cerebral ischemia in rats (Endoh et al., Neurosci. Lett. 154, 125-128, 1993; Endoh et al., Brain Res. 651, 92-100, 1994; Nagafuji et al., in Brain Edema IX (Ito et al, eds.), 60, pp285-288, 1994, Springer-Verlag; Toshiaki NAGAFUJI and Toru MATSUI, Jikken Igaku, 13, 127-135, 1995; Nagafuji et al., Mol. Chem. Neuropathol. 26, 107-157, 1995).
These reports suggest that N-CNOS or iNOS may be closely involved in the mechanism for the occurrence and the development of the tissue damage following cerebral ischemia.
Referring now to NO, it is at least one of the essences of endothelium-derived relaxing factor (EDRF) and, hence, is believed to take part in the adjustment of the tension of blood vessels and the blood flow (Moncada et al., Pharmacol. Rev. 43, 109-142, 1991). As a matter of fact, it was reported that when rats were administered high doses of L-NNA, the cerebral blood flow was found to decrease in a dose-dependent manner as the blood pressure increased (Toru MATSUI et al., Jikken Igaku, 11, 55-60, 1993). The brain has a mechanism by which the cerebral blood flow is maintained at a constant level notwithstanding the variations of blood pressure over a specified range (which is commonly referred to as xe2x80x9cautoregulation mechanismxe2x80x9d) (xe2x80x9cNOSOTCHU JIKKEN HANDBOOKxe2x80x9d, compiled by Keiji SANO, published by IPC, 247-249, 1990). The report of Matsui et al. suggests the failure of this xe2x80x9cautoregulation mechanismxe2x80x9d to operate. Therefore, if E-cNOS is particularly inhibited beyond a certain limit in an episode of brain ischemia, the cerebral blood flow will decrease and the blood pressure will increase, thereby aggravating the dynamics of microcirculation, possibly leading to an expansion of the ischemic lesion.
The present inventors previously found that NG-nitro-L-arginine (L-NNA), known to be a NOS inhibitor, possessd ameliorative effects against brain edema and infarction in a rat model of focal cerebral ischemia (Nagafuji et al., Neurosci. Lett. 147, 159-162, 1992; Japanese Patent Public Disclosure No. 192080/1994), as well as the neuronal cell death in a gerbil model of forebrain ischemia (Nagafuji et al., Eur. J. Pharmacol. Env. Tox. 248, 325-328, 1993). On the other hand, relatively high doses of NOS inhibitors have been reported to be entirely ineffective against ischemic brain damage or sometimes aggravating it (Iadecola et al., J. Cereb. Blood Flow Metab. 14, 175-192, 1994; Toshiaki NAGAFUJI and Toru MATSUI, Jikken Igaku, 13, 127-135, 1995; Nagafuji et al., Mol. Chem. Neuropathol. 26, 107-157, 1995). It should be noted that as a matter of fact, all papers that reported the changes of NO or its metabolites in the brain after permanent or temporary cerebral ischemia agreed in their results to show the increase in the levels of those substances (Toshiaki NAGAFUJI and Toru MATSUI, Jikken Igaku, 13, 127-135, 1995; Nagafuji et al., Mol. Chem. Neuropathol. 26, 107-157, 1995).
One of the reasons for explaining the fact that conflicting reports have been made about the effectiveness of NOS inhibitors in cerebral ischemic models would be the low selectivity of the employed NOS inhibitors for N-cNOS or iNOS. As a matter of fact, no existing NOS inhibitors including L-NNA and L-NAME have a highly selective inhibitory effect on a specific NOS isoform (Nagafuji et al., Neuroreport 6, 1541-1545, 1995; Nagafuji et al., Mol. Chem. Neuropathol. 26, 107-157, 1995). Therefore, it may well be concluded that desirable therapeutics of ischemic cerebrovascular diseases should have a selective inhibitory effect on N-cNOS or iNOS (Nowicki et al., Eur. J. Pharmacol. 204, 339-340, 1991; Dawson et al., Proc. Natl. Acad. Sci. USA 88, 6368-6371, 1991; Iadecola et al., J. Cereb. Blood Flow Metab. 15, 52-59, 1995; Iadecola et al., J. Cereb. Blood Flow Metab. 15, 378-384, 1995; Toshiaki NAGAFUJI and Toru MATSUI, Jikken Igaku 13, 127-135, 1995; Nagafuji et al., Mol. Chem. Neuropathol. 26, 107-157, 1995).
It has also been suggested that N-cNOS inhibitors have the potential for use as therapeutics of traumatic brain injuries (Oury et al., J. Biol. Chem. 268, 15394-15398, 1993; MacKenzie et al., Neuroreport 6, 1789-1794, 1995), seizure (Rigaud-Monnet et al., J. Cereb. Blood Flow Metab. 14, 581-590; 1994), headache and other pains (Moore et al., Br. J. Pharmacol. 102, 198-202, 1991; Olesen., Trends Pharmacol. 15, 149-153, 1994), morphine tolerance and dependence (Kolesnikov et al., Eur. J. Pharmacol. 221, 399-400, 1992; Cappendijk et al., Neurosci. Lett. 162, 97-100, 1993), Alzheimer""s disease (Hu and EI-FaKahany, Neuroreport 4, 760-762, 1993; Meda et al., Nature 374, 647-650, 1995) and Parkinson""s disease (Youdim et al., Advances Neurol. 60, 259-266, 1993; Schulz et al., J. Neurochem. 64, 936-939, 1995).
Upon stimulation by certain kinds of cytokines and/or LPS, iNOS is induced in immunocytes such as macrophages and glial cells and other cells, and the resulting large amount of NO will dilate blood vessels to cause a fatal drop in blood pressure. Therefore, it is speculated that an iNOS inhibitor may be effective against septic shocks (Kilbourn and Griffith, J. Natl. Cncer Inst. 84, 827-831, 1992; Cobb et al., Crit. Care Med. 21, 1261-1263, 1993; Lorente et al., Crit. Care Med. 21, 1287-1295, 1993).
Further, it has been suggested that iNOS inhibitors are useful as therapeutics of chronic rheumatoid arthritis and osteoarthritis (Farrell et al., Ann, Rheum. Dis. 51, 1219-1222, 1992; Hauselmann et al., FEBS Lett. 352, 361-364, 1994; Islante et al., Br. J. Pharmacol. 110, 701-706, 1993), viral or nonviral infections (Zembvitz and Vane, Proc. Natl. Acad. Sci. USA 89, 2051-2055, 1992; Koprowski et al., Proc. Natl. Acad. Sci. USA 90, 3024-3027, 1993) and diabetes (Kolb et al., Life Sci. PL213-PL217, 1991).
The NOS inhibitors so far reported to have selectivity for N-cNOS are NG-cyclpropyl-L-arginine (L-CPA) (Lamberte et al., Eur. J. Pharmacol. 216, 131-134, 1992), L-NNA (Furfine et al., Biochem. 32, 8512-8517, 1993), S-methyl-L-thiocitrulline (L-MIN) (Narayanan and Griffith, J. Med. Chem. 37, 885-887, 1994; Furfine et al., J. Biol. Chem. 37, 885-887, 1994; Furfine et al., J. Biol. Chem. 269, 26677-26683, 1994; W095/09619; Narayanan et al., J. Biol. Chem. 270, 11103-11110, 1995; Nagafuji et al., Neuroreport 6, 1541-1545, 1995) and S-ethyl-L-thiocitrulline (L-EIN) (Furfine et al., J. Biol. Chem. 269, 26677-26683, 1994; W095/09619; Narayanan et al., J. Biol. Chem. 270, 11103-11110, 1995).
In addition, the inhibitors that have been reported to have selectivity for iNOS are NG-iminoethyl-L-ornithine (L-NIO) (McCall et al., Br. J. Pharmacol. 102, 234-238, 1991) and aminoguanidine (AG) (Griffith et al., Br. J. Pharmacol. 110, 963-968, 1993; Hasan et al. Eur. J. Pharmacol. 249, 101-106, 1993)
An object of the present invention is to provide novel compounds that have a selective inhibitory effect on calcium-dependent NOS which is present constitutively in the brain, particularly in neurons (N-cNOS), or an apparently calcium-independent and inducible NOS (iNOS) and which are useful as therapeutics of cerebrovascular diseases, Alzheimer""s disease, analgesics, morphine tolerance or dependence, sepsis, chronic rheumatoid arthritis, osteoarthritis, viral or nonviral infections, diabetes and Parkinson""s disease.
As a result of the intensive studies made in order to attain the stated object, the present inventors found that N-substituted aniline derivatives represented by the general formula (1), or possible stereoisomers or optically active forms of the compounds, as well as pharmaceutically acceptable salts thereof have an inhibitory effect against or selectivity for N-cNOS or iNOS that are superior to the existing NOS inhibitors, thereby exhibiting marked effectiveness as therapeutics of cerebrovascular diseases (especially as therapeutics of occlusive cerebrovascular diseases):

 
(where
R1 is SR6 or NR7R8;
where R6 is an optionally substituted straight-chained or branched alkyl group having 1-6 carbon atoms or a straight-chained or branched alkenyl group having 2-6 carbon atoms;
R7 is a hydrogen atom, a straight-chained or branched alkyl group having 1-6 carbon atoms, a cyclic alkyl group having 3-8 carbon atoms, a straight-chained or branched alkenyl group having 2-6 carbon atoms, a straight-chained or branched alkynyl group having 3-6 carbon atoms, a straight-chained or branched alkoxy group having 1-6 carbon atoms, a straight-chained or branched alkyl group having 1-6 carbon atoms, or a nitro group;
R8 is a hydrogen atom or a straight-chained or branched alkyl group having 1-6 carbon atoms;
R2 is a hydrogen atom, a straight-chained or branched alkyl group having 1-6 carbon atoms, an alkoxycarbonyl group of which the alkyl portion is a straight-chained or branched alkyl group having 1-6 carbon atoms or a carboxyl group, or may combine with R3 to form a 3- to 8-membered ring;
R3 is a hydrogen atom or a straight-chained or branched alkyl group having 1-6 carbon atoms, or may combine with R2 to form a 3- to 8-membered ring;
R4 is a hydrogen atom, a straight-chained or branched alkyl group having 1-6 carbon atoms, an alkoxycarbonyl group of which the alkyl portion is a straight-chained or branched alkyl group having 1-6 carbon atoms, an optionally substituted acyl group having 1-8 carbon atoms, an amidino group that may be substituted on the nitrogen atom with a straight-chained or branched alkyl group having 1-6 carbon atoms or a cyclic alkyl group having 3-8 carbon atoms or a nitro group, or may combine with R5 to form a 3- to 8-membered ring;
R5 is a hydrogen atom, a straight-chained or branched alkyl group having 1-6 carbon atoms, an alkoxycarbonyl group of which the alkyl portion is a straight-chained or branched alkyl group having 1-6 carbon atoms, an alkoxycabonylamino group of which the alkyl portion is a straight-chained or branched alkyl group having 1-6 carbon atoms or an amino group, or may combine with R4 to form a 3- to 8-membered ring;
Y1, Y2, Y3 and Y4 which may be the same or different are each a hydrogen atom, a halogen atom, a nitro group, a cyano group, a hydroxyl group, a straight-chained or branched alkyl group having 1-6 carbon atoms that may be substituted by 1-3 halogen atoms, a cyclic alkyl group having 3-6 carbon atoms that may be substituted by 1-3 halogen atoms, a straight-chained or branched alkenyl group having 2-6 carbon atoms, a straight-chained or branched alkynyl group having 2-6 carbon atoms, an optionally substituted straight-chained or branched alkoxy group having 1-6 carbon atoms, a straight-chained or branched alkylthio group having 1-6 carbon atoms, NY5Y6, or COY7;
where Y5 and Y6 which may be the same or different are each a hydrogen atom, an optionally substituted straight-chained or branched alkyl group having 1-6 carbon atoms, or an optionally substituted cyclic alkyl group having 3-6 carbon atoms, an acyl group having 1-8 carbon atoms, an alkoxycarbonyl group of which the alkyl portion is a straight-chained or branched alkyl group having 1-6 carbon atoms, or Y5 and Y6 may combine together to form a 3- to 8-membered ring;
Y7 is a hydrogen atom, a hydroxyl group, a straight-chained or branched alkyl group having 1-6 carbon atoms or a cyclic alkyl group having 3-6 carbon atoms, an alkoxy group of which the alkyl portion is a straight-chained or branched alkyl group having 1-6 carbon atoms or NY5Y6;
where Y5 and Y6 which may be the same or different are each a hydrogen atom, a straight-chained or branched alkyl group having 1-6 carbon atoms or a cyclic alkyl group having 3-6 carbon atoms; and
n and m are each an integer of 0 or 1).
The present invention has been accomplished on the basis of this finding.
The present inventors also found that compounds represented by the general formula (21) are intermediates useful in the synthesis of the compounds represented by the general formula (1):

 
(where
R2 is a hydrogen atom, a straight-chained or branched alkyl group having 1-6 carbon atoms or may combine with R3 to form a 3- to 8-membered ring;
R3 is a straight-chained or branched alkyl group having 1-6 carbon atoms or may combine with R2 to form a 3- to 8-membered ring;
Y1, Y2, Y3 and Y4 which may be the same or different are each a hydrogen atom, a halogen atom, a straight-chained or branched alkyl group having 1-6 carbon atoms that may be substituted by 1-3 halogen atoms, a cyclic alkyl group having 3-6 carbon atoms that may be substituted by 1-3 halogen atoms, a straight-chained or branched alkoxy groups having 1-6 carbon atoms of which the alkyl portion may optionally have a substituent, a straight-chained or branched alkylthio group having 1-6 carbon atoms, NY5Y6 or COY7;
where Y5 and Y6 which may be the same or different are each a hydrogen atom, an optionally substituted straight-chained or branched alkyl group having 1-6 carbon atoms, an acyl group having 1-8 carbon atoms or an alkoxycarbonyl group of which the alkyl portion is a straight-chained or branched alkyl group having 1-6 carbon atoms or, alternatively, Y5 and Y6 may combine together to form a 3- to 8-membered ring;
Y7 is a hydrogen atom, a straight-chained or branched alkyl group having 1-6 carbon atoms, a cyclic alkyl group having 3-6 carbon atoms, a straight-chained or branched alkoxy group having 1-6 carbon atoms, or NY5Y6;
where Y5 and Y6 which may be the same or different are each a hydrogen atom, a straight-chained or branched alkyl group having 1-6 carbon atoms, or a cyclic alkyl group having 3-6 carbon atoms).
Japanese Patent Public Disclosure No. 13391/1975 ; Clin. Sci. Mol. Med. 53, 355-364, 1977; J. Chem. Eng. Data, 22, 3, 224-245, 1977; Clin. Sci. Mol. Med. 54, 673-677, 1978; J. Biochem. 94, 123-128, 1983 and International Publication WO94/21621 teach compounds that are related to the compounds of the invention which are represented by the general formula (1).
In addition, part of the compounds of the invention which are represented by the general formula (1) are described by generic concept in Japanese Patent Public Disclosure Nos. 97933/1977, 99227/1977 and 158249/1987. However, these patents make no reference whatsoever to the NOS inhibiting action of the compounds corresponding to those of the invention or other aspects thereof such as their use as therapeutics of cerebro-vascular diseases, traumatic brain injuries, seizure, Alzheimer""s disease, Parkinson""s disease, headache and other pains, morphine tolerance or dependence, septic shocks, chronic rheumatoid arthritis, osteoarthritis, viral or antiviral infections and diabetes.
It should also be noted that International Publication WO95/00505 which was not published before the priority date of the subject application (Dec. 12, 1994) but which was later published, and J. Chem. Soc. Perkin Trans. 1, 2025-2030, 1977 describe part of the compounds of the invention which are represented by the general formula (1), and said International Publication also shows part of the compounds of the invention by generic concept.
Further in addition, International Publication WO95/09619 which was not published before the priority date of the subject application (Dec. 12, 1994) but which was later published shows part of the compounds of the invention of the general formula (1) by generic concept.
As it will be demonstrated by the tests hereinafter, the compounds described in the Examples of the invention have by far superior NOS inhibiting action, as well as extremely high selectivity for both N-cNOS and iNOS compared to the compounds described in International Publication WO95/00505 and WO95/09619.